Radial Angle Detection Device for Electric Power Steering
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Solution Overview
Problem
Conventional angle detection devices face challenges in enhancing accuracy without increasing size, as the configuration with a sensor magnet at the rotating shaft end provides high accuracy but results in a large axial dimension, while arranging the sensor magnet around the shaft leads to increased spatial magnetic field distortion and reduced accuracy.
Innovation Solution
An angle detection device with sensors positioned 90 degrees apart, outputting signals corresponding to the magnetic field, which reduces higher harmonic components of the spatial magnetic field and output voltage, thereby enhancing detection accuracy without enlarging the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor magnet is arranged at the rotating shaft end and the magnetoresistive semiconductor sensor is arranged opposite to the sensor magnet in the axis direction, then angle detection accuracy is improved, but axial dimension increases
Solution Approach 1:
The patent transitions the sensor arrangement from an axial configuration (sensor magnet at shaft end, sensor opposite in axis direction) to a radial configuration (sensor magnet around shaft circumference, sensor around magnet). This dimensional change allows the system to maintain angle detection accuracy while reducing axial dimension, as the magnetic field interaction occurs in the radial plane rather than along the axial direction.
Solution Approach 2:
The patent inverts the conventional arrangement by placing the sensor magnet around the shaft circumference rather than at the shaft end, and positioning the sensor around the magnet rather than opposite it in the axial direction. This inversion resolves the contradiction by achieving accurate angle detection through radial field interaction while minimizing axial space requirements.
2Length of stationary object
If the sensor magnet is arranged around the rotating shaft and the magnetoresistive semiconductor sensor is arranged around the sensor magnet, then axial dimension is reduced, but spatial magnetic field distortion increases and angle detection accuracy deteriorates
Solution Approach 1:
The patent applies local quality by strategically positioning multiple sensors around the shaft circumference at specific angular intervals (e.g., 90 degrees apart). Each sensor detects the magnetic field at its specific location, and the combination of these localized measurements compensates for spatial magnetic field distortion, maintaining angle detection accuracy while using the compact radial arrangement.
Solution Approach 2:
The patent changes the detection parameters by using multiple sensors at different angular positions rather than a single sensor. This parameter change allows the system to process multiple magnetic field measurements and calculate the angle through signal processing, thereby compensating for spatial distortion and maintaining accuracy in the compact radial configuration.
3Measurement precision
If multiple sensors are arranged at positions separated by 90 degrees to reduce higher harmonic components, then angle detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the angle detection function by using multiple sensors positioned at specific angular intervals (e.g., 90 degrees apart) around the shaft circumference. Each sensor segment detects the magnetic field at its position, and the combined signals from these segmented measurements reduce higher harmonic components and improve angle detection accuracy through signal processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed configuration effectively reduces angle detection errors, achieving higher accuracy by averaging signals from sensors positioned 90 degrees apart, minimizing 2nd and 4th order angle errors, and maintaining a compact structure.
Implementation Method 1
The magnetoresistive semiconductor sensor increases a changing rate of electrical resistance by a bias magnetic field and detects the angle of rotation by the direction of the magnetic field
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Included are: a sensor magnet (2) which rotates integrally with a rotating shaft (1) centering on the rotating shaft (1), and generates a magnetic field for angle detection which is for detecting the angle of rotation; a first sensor (10a) and a second sensor (10b) each of which is arranged opposite to the sensor magnet (2) at a position separated in angle by 90 [deg] on the circumference centered on the rotating shaft (1), and outputs a signal corresponding to the magnetic field for angle detection; and an angle calculator (13) that calculates a rotation angle by using the signals from the first sensor (10a) and the second sensor (10b).